Windows Store App - navigation - keep ViewModels alive

I'm trying my hands on using MVVM for a windows store app and out of the box at every navigation (using INavigationService) the viewmodel gets recreated, now I can see this being a problem in my case, is there a clever way of persisting the ViewModels or is
the only way to extend the default implementation of the navigation service?

Any suggestions appreciated.

P.S. I haven't touched Catel in a while and I love the fact that it's still actively worked on and improved with every tick, well done.

thank you for the quick reply. What I've done is inherited Catels ViewModelFactory and overriden the 'CreateViewModel' method to catch created viewmodels and then return an already created one if exists. Registered in the ServiceLocator but now when the App
starts on the constructor of 'MainPage' I get the following exception:

Now I've looked through the source code and I think what happens is that LogicBase has a field:

private readonly IViewModelFactory _viewModelFactory;

Which gets a reference to the old service before I register my type? Correct me if I'm wrong please. I register my service by an instance (didn't work well with type for some reason) as early as possible I think:

public App()
{
var service = new Services.PersistentViewModelFactory((Catel.IoC.TypeFactory)Catel.IoC.ServiceLocator.Default.GetService(typeof(Catel.IoC.ITypeFactory)));
Catel.IoC.ServiceLocator.Default.RegisterInstance<Catel.MVVM.IViewModelFactory>(service);

Strange, I use a customized ViewModelFactory a lot and it normally works. Each LogicBase determines the IViewModelFactory as soon as it is being created. The only reason I can think of is that you are not registering the customized view model factory soon
enough. Make sure that you do it before any views are loaded.

Now I'm all for saving the ViewModel on navigation (might be some exceptions) but closing at the same time is not really great in my scenario. Unfortunately the navigation logic is a private field in the Page class so I can't really change any behaviour and
my custom factory is all well and fine but every view model gets closed on the first navigation.

I really don't want to inherit/rewrite the Page and/or NavigationPageLogic class if there is something else that I could do? Ideally what would be nice is for Catel to provide a way to customise behaviour on a per view basis (should it just save, cancel and
close or save and close) on navigation.